package acm.pta7;

import java.util.Scanner;

public class 倒数第n个字符串 {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        long num= (long) Math.pow(26,n);
        num=num-k;
        StringBuilder sb=new StringBuilder();
        while (n-->0){
            long pow = (long) Math.pow(26, n);
            sb.append((char) (97+num/pow));
            num%=pow;
        }
        System.out.println(sb);
    }
}
